Field of the Invention
The present invention relates to an image forming apparatus, such as a copier, a printer, and a facsimile machine, and to a developer container, a developing device, and a process cartridge for use in the image forming apparatus.
Description of the Related Art
An image forming apparatus employing an electrophotographic process includes a developing device that forms a developer image by supplying a developer to an electrostatic latent image formed by scanning exposure performed on an image carrier. Nowadays, the developing device is often integrally accommodated as a process cartridge together with the image carrier and other process units (e.g., charging member). When they are integrally formed as the process cartridge and this process cartridge is detachably attached to a main body of the apparatus, as described above, an operation of supplying the developer and a maintenance operation are facilitated.
In this process cartridge system, when the developer runs out, a user replaces the cartridge and replenishes the developer, thus enabling the apparatus to be able to form an image again. Such an image forming apparatus typically includes a unit configured to detect a state where the developer has run out and signal a user to replace it, that is, a developer remaining amount detecting unit.
One example of the developer remaining amount detecting unit is the one employing a plate antenna process proposed in Japanese Patent Laid-Open No. 2001-117346. This process uses a pair of input-side and output-side electrodes, measures capacitance between both of the electrodes, and detects the amount of the developer.
Japanese Patent Laid-Open No. 2003-248371 proposes a configuration in which a developer bearing member is considered as an input-side electrode by application of an alternating-current bias thereto and a capacitance detector being an output-side electrode is arranged in a location opposed to the developer bearing member inside a developing device.
The capacitance between the capacitance detector and the developer bearing member employs changing in accordance with the amount of the developer, for example, insulating toner. That is, if a space between the capacitance detector and the developer bearing member is filled with the developer, the capacitance therebetween is large. As the amount of the developer reduces, the proportion of air that occupies the space therebetween increases and the capacitance decreases. Accordingly, if a relationship between the amount of the developer and the capacitance between the developer bearing member and metal plates being the capacitance detector or the capacitance between the metal plates and is determined in advance, the present amount of the developer in the developing device in use can be detected by measurement of the capacitance.
Japanese Patent Laid-Open No. 2002-40906 discloses, as a method of fixing a plate antenna, a case where an antenna member is affixed to a cartridge frame using two-sided adhesive tape and a configuration in which processing, such as depositing or printing, is directly performed on the frame. In addition, that patent literature also discloses a configuration in which the frame and the electrodes are formed by coinjection molding using a resin for forming the frame and a conductive resin for the electrodes.
The above-described techniques of detecting the amount of the developer by measuring the capacitance between the electrodes need metal wiring from the detection electrodes. The arrangement of that wiring tends to be complex.